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Weibull++ 7 Case Studies

 


Case Study 4 - Degradation Analysis Example 

Software Used: 
Weibull++ 7


Background
Five turbine blades were tested for crack propagation. The test units were cyclically stressed and inspected every 100,000 cycles for crack length. Failure is defined as a crack of length 30 mm or greater.

Using Weibull++ 7's Degradation Analysis module and Quick Calculation Pad, determine the B10 life for the blades using degradation analysis with an exponential model for the extrapolation. 

Experiment and Data
The table shown next displays the test results for the five units at each cycle. 

Cycle (x100) Unit A Unit B Unit C Unit D Unit E
100 15mm 10mm 17mm 12mm 10mm
200 20mm 15mm 25mm 16mm 15mm
300 22mm 20mm 26mm 17mm 20mm
400 26mm 25mm 27mm 20mm 26mm
500 29mm 30mm 33mm 26mm 33mm

Analysis
Step 1:
Using Weibull++ 7, create a Degradation Analysis Folio and enter the data into the Data sheet. Select Exponential for the model and enter 30 for the Critical Degradation, as shown next.

Times-to-failure data for each unit in Weibull++'s Degradation Analysis Folio

Calculate the parameters. To view them, click the Show Fit Parameters button in the Control Panel. The parameter results will appear in the Results Panel, as shown next.

Parameter results

Step 2: Next, plot the data from the degradation analysis, as shown next.

Degradation vs. Time plot

Step 3: Transfer the extrapolated failure times from the Degradation Analysis Folio to a new Standard Folio. Analyze the data using the 2-parameter Weibull distribution and MLE, as shown next.

Parameters calculated for the extrapolated failure times

Step 4: Using the QCP, the B(10) life is calculated to be 399,597 cycles, as shown next. 

ReliaSoft's QCP used to calculate the B10 life

 

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